/*-
 * See the file LICENSE for redistribution information.
 *
 * Copyright (c) 2002,2007 Oracle.  All rights reserved.
 *
 * $Id: LogUtils.java,v 1.50.2.1 2007/02/01 14:49:47 cwl Exp $
 */

package com.sleepycatje.je.log;

import java.nio.ByteBuffer;
import java.sql.Timestamp;

import javax.transaction.xa.Xid;

/**
 * This class holds convenience methods for marshalling internal JE data to and
 * from the log.
 */
public class LogUtils {
    /* Storage sizes for int, long in log. */
    public static final int SHORT_BYTES = 2;
    public static final int INT_BYTES = 4;
    public static final int LONG_BYTES = 8;
    public static final int UNSIGNED_INT_BYTES = 4;

    private static final boolean DEBUG = false;

    /*
     * We can return the same byte[] for 0 length arrays.
     */
    public static final byte[] ZERO_LENGTH_BYTE_ARRAY = new byte[0];

    /**
     * Marshall a long into the next 4 bytes in this buffer. Necessary when the
     * long is used to hold an unsigned int.
     */
    public static void writeUnsignedInt(ByteBuffer buf, long value) {
        buf.put((byte) (value >>> 0));
        buf.put((byte) (value >>> 8));
        buf.put((byte) (value >>> 16));
        buf.put((byte) (value >>> 24));
    }

    /**
     * Unmarshall the next four bytes which hold an unsigned int into a long.
     */
    public static long getUnsignedInt(ByteBuffer buf) {
	long ret = (buf.get() & 0xFFL) << 0;
	ret += (buf.get() & 0xFFL) << 8;
	ret += (buf.get() & 0xFFL) << 16;
	ret += (buf.get() & 0xFFL) << 24;
	return ret;
    }

    /*
     * Marshall objects.
     */

    /**
     * Write a short into the log.
     */
    public static void writeShort(ByteBuffer logBuf, short i) {
        byte b = (byte) ((i >> 0) & 0xff);
        logBuf.put(b);
        b = (byte) ((i >> 8) & 0xff);
        logBuf.put(b);
    }

    /**
     * Read a short from the log.
     */
    public static short readShort(ByteBuffer logBuf) {
        return (short) (((logBuf.get() & 0xFF) << 0) +
                        ((logBuf.get() & 0xFF) << 8));
    }

    /**
     * Write an int into the log.
     */
    public static void writeInt(ByteBuffer logBuf, int i) {
        byte b = (byte) ((i >> 0) & 0xff);
        logBuf.put(b);
        b = (byte) ((i >> 8) & 0xff);
        logBuf.put(b);
        b = (byte) ((i >> 16) & 0xff);
        logBuf.put(b);
        b = (byte) ((i >> 24) & 0xff);
        logBuf.put(b);
    }

    /**
     * Read a int from the log.
     */
    public static int readInt(ByteBuffer logBuf) {
	int ret = (logBuf.get() & 0xFF) << 0;
	ret += (logBuf.get() & 0xFF) << 8;
	ret += (logBuf.get() & 0xFF) << 16;
	ret += (logBuf.get() & 0xFF) << 24;
	return ret;
    }

    /**
     * @return log storage size for a byteArray.
     */
    public static int getIntLogSize() {
        return INT_BYTES;
    }

    /**
     * Write an int into the log in MSB order.  Used for ordered keys.
     */
    public static void writeIntMSB(ByteBuffer logBuf, int i) {
        byte b = (byte) ((i >> 24) & 0xff);
        logBuf.put(b);
        b = (byte) ((i >> 16) & 0xff);
        logBuf.put(b);
        b = (byte) ((i >> 8) & 0xff);
        logBuf.put(b);
        b = (byte) ((i >> 0) & 0xff);
        logBuf.put(b);
    }

    /**
     * Read a int from the log in MSB order.  Used for ordered keys.
     */
    public static int readIntMSB(ByteBuffer logBuf) {
	int ret = (logBuf.get() & 0xFF) << 24;
	ret += (logBuf.get() & 0xFF) << 16;
	ret += (logBuf.get() & 0xFF) << 8;
	ret += (logBuf.get() & 0xFF) << 0;
	return ret;
    }

    /**
     * Write a long into the log.
     */
    public static void writeLong(ByteBuffer logBuf, long l) {
        byte b =(byte) (l >>> 0);
        logBuf.put(b);
        b =(byte) (l >>> 8);
        logBuf.put(b);
        b =(byte) (l >>> 16);
        logBuf.put(b);
        b =(byte) (l >>> 24);
        logBuf.put(b);
        b =(byte) (l >>> 32);
        logBuf.put(b);
        b =(byte) (l >>> 40);
        logBuf.put(b);
        b =(byte) (l >>> 48);
        logBuf.put(b);
        b =(byte) (l >>> 56);
        logBuf.put(b);
    }

    /**
     * Read a long from the log.
     */
    public static long readLong(ByteBuffer logBuf) {
	long ret = (logBuf.get() & 0xFFL) << 0;
	ret += (logBuf.get() & 0xFFL) << 8;
	ret += (logBuf.get() & 0xFFL) << 16;
	ret += (logBuf.get() & 0xFFL) << 24;
	ret += (logBuf.get() & 0xFFL) << 32;
	ret += (logBuf.get() & 0xFFL) << 40;
	ret += (logBuf.get() & 0xFFL) << 48;
	ret += (logBuf.get() & 0xFFL) << 56;
	return ret;
    }

    /**
     * @return log storage size for a byteArray.
     */
    public static int getLongLogSize() {
        return LONG_BYTES;
    }

    /**
     * Write a byte array into the log. The size is stored first as an integer.
     */
    public static void writeByteArray(ByteBuffer logBuf,
                                      byte[] b) {

        /* Write the length. */
        writeInt(logBuf, b.length);

        /* Add the data itself. */
        logBuf.put(b);                     // data
    }

    /**
     * Read a byte array from the log. The size is stored first as an integer.
     */
    public static byte[] readByteArray(ByteBuffer logBuf) {
        int size = readInt(logBuf);  // how long is it?
        if (DEBUG) {
            System.out.println("pos = " + logBuf.position() +
                               " byteArray is " + size + " on read");
        }
	if (size == 0) {
	    return ZERO_LENGTH_BYTE_ARRAY;
	}
        byte[] b = new byte[size];  
        logBuf.get(b);               // read it out
        return b;                  
    }

    /**
     * @return log storage size for a byteArray
     */
    public static int getByteArrayLogSize(byte[] b) {
        return INT_BYTES + b.length;
    }

    /**
     * writeString and readString should both use something other than the
     * default character encoding (e.g. UTF-8).  But since switching now might
     * cause incompatibilities with existing databases, we need to do something
     * more complicated than just add "UTF-8" to the getBytes and "new
     * String()" calls below.  User-defined character strings are encoded using
     * these methods when XA is used.  See [#15293].
     */

    /**
     * Write a string into the log. The size is stored first as an integer.
     */
    public static void writeString(ByteBuffer logBuf,
                                   String stringVal) {
        writeByteArray(logBuf, stringVal.getBytes());
    }

    /**
     * Read a string from the log. The size is stored first as an integer.
     */
    public static String readString(ByteBuffer logBuf) {
        return new String(readByteArray(logBuf));
    }

    /**
     * @return log storage size for a string
     */
    public static int getStringLogSize(String s) {
        return INT_BYTES + s.getBytes().length;
    }

    /**
     * Write a timestamp into the log.
     */
    public static void writeTimestamp(ByteBuffer logBuf,
                                      Timestamp time) {
        writeLong(logBuf, time.getTime());
    }

    /**
     * Read a timestamp from the log.
     */
    public static Timestamp readTimestamp(ByteBuffer logBuf) {
        long millis = readLong(logBuf);
        return new Timestamp(millis);
    }

    /**
     * @return log storage size for a timestamp
     */
    public static int getTimestampLogSize() {
        return LONG_BYTES;
    }

    /**
     * Write a boolean into the log.
     */
    public static void writeBoolean(ByteBuffer logBuf,
                                    boolean bool) {
        byte val = bool ? (byte) 1 : (byte) 0;
        logBuf.put(val);
    }

    /**
     * Read a boolean from the log.
     */
    public static boolean readBoolean(ByteBuffer logBuf) {
        byte val = logBuf.get();
        return (val == (byte) 1) ? true : false;
    }

    /**
     * @return log storage size for a boolean.
     */
    public static int getBooleanLogSize() {
        return 1;
    }

    /*
     * Dumping support.
     */
    public static boolean dumpBoolean(ByteBuffer itemBuffer, StringBuffer sb,
                                      String tag) {
        sb.append("<");
        sb.append(tag);
        sb.append(" exists = \"");
        boolean exists = readBoolean(itemBuffer);
        sb.append(exists);
        if (exists) {
            sb.append("\">");
        } else {
            /* Close off the tag, we're done. */
            sb.append("\"/>");
        }
        return exists;
    }

    /**
     * The byte[]'s in Xid's are known to be 255 or less in length.  So instead
     * of using read/writeByteArray(), we can save 6 bytes per record by making
     * the byte[] length be 1 byte instead of 4.
     */
    public static int getXidSize(Xid xid) {
	byte[] gid = xid.getGlobalTransactionId();
	byte[] bqual = xid.getBranchQualifier();
	return
	    INT_BYTES +                         // FormatId
	    1 +                                 // gxid length byte
	    1 +                                 // bqual length byte
	    (gid == null ? 0 : gid.length) +    // gid bytes
	    (bqual == null ? 0 : bqual.length); // bqual bytes
    }

    /*
     * Xid.gid[] and bqual[] can't be longer than 64 bytes so we can get away
     * with writing the length in one byte, rather than 4.
     */
    public static void writeXid(ByteBuffer logBuf, Xid xid) {
	byte[] gid = xid.getGlobalTransactionId();
	byte[] bqual = xid.getBranchQualifier();

	writeInt(logBuf, xid.getFormatId());

	if (gid == null) {
	    logBuf.put((byte) -1);
	} else {
	    logBuf.put((byte) (gid.length));
	    logBuf.put(gid);
	}

	if (bqual == null) {
	    logBuf.put((byte) -1);
	} else {
	    logBuf.put((byte) (bqual.length));
	    logBuf.put(bqual);
	}
    }

    /*
     * Xid.gid[] and bqual[] can't be longer than 64 bytes so we can get away
     * with writing the length in one byte, rather than 4.
     */
    public static Xid readXid(ByteBuffer logBuf) {
	int formatId = readInt(logBuf);

	int gidLen = logBuf.get();
	byte[] gid = null;
	if (gidLen >= 0) {
	    gid = new byte[gidLen];
	    logBuf.get(gid);
	}

	int bqualLen = logBuf.get();
	byte[] bqual = null;
	if (bqualLen >= 0) {
	    bqual = new byte[bqualLen];
	    logBuf.get(bqual);
	}

	return new XidImpl(formatId, gid, bqual);
    }

    public static class XidImpl implements Xid {
	private int formatId;
	private byte[] gid;
	private byte[] bqual;

	/* public for unit tests. */
	public XidImpl(int formatId, byte[] gid, byte[] bqual) {
	    this.formatId = formatId;
	    this.gid = gid;
	    this.bqual = bqual;
	}

	public int getFormatId() {
	    return formatId;
	}

	public byte[] getGlobalTransactionId() {
	    return gid;
	}

	public byte[] getBranchQualifier() {
	    return bqual;
	}

	public boolean equals(Object o) {
	    if (!(o instanceof XidImpl)) {
		return false;
	    }

	    XidImpl xid = (XidImpl) o;
	    if (xid.getFormatId() != formatId) {
		return false;
	    }
	    if (compareByteArrays(xid.getGlobalTransactionId(), gid) &&
		compareByteArrays(xid.getBranchQualifier(), bqual)) {
		return true;
	    }

	    return false;
	}

	public int hashCode() {
	    int code = formatId;
	    if (gid != null) {
		for (int i = 0; i < gid.length; i++) {
		    code += gid[i];
		}
	    }
	    if (bqual != null) {
		for (int i = 0; i < bqual.length; i++) {
		    code += bqual[i];
		}
	    }
	    return code;
	}

	private boolean compareByteArrays(byte[] b1, byte[] b2) {
	    if (b1 == null ||
		b2 == null) {
		return b1 == b2;
	    }

	    if (b1.length != b2.length) {
		return false;
	    }

	    for (int i = 0; i < b1.length; i++) {
		if (b1[i] != b2[i]) {
		    return false;
		}
	    }

	    return true;
	}

	public String toString() {
	    StringBuffer sb = new StringBuffer();
	    sb.append("<Xid formatId=\"").append(formatId);
	    sb.append("\" gTxnId=\"");
	    if (gid == null) {
		sb.append("null");
	    } else {
		sb.append(new String(gid));
	    }
	    sb.append("\" bqual=\"");
	    if (bqual == null) {
		sb.append("null");
	    } else {
		sb.append(new String(bqual));
	    }
	    sb.append("\"/>");
	    return sb.toString();
	}
    }
}
